1. Field of the Invention
The present invention relates to a turbo compressor and a refrigerator. More specifically, the present invention relates to a turbo compressor capable of compressing a fluid by a plurality of impellers and a refrigerator including the turbo compressor.
Priority is claimed on Japanese Patent Application No. 2009-170192, filed Jul. 21, 2009, the content of which is incorporated herein by reference.
2. Description of Related Art
As a refrigerator for cooling or refrigerating a material to be cooled such as water, there is known a turbo refrigerator or the like including a turbo compressor which compresses and discharges the refrigerant by means of a compressing means equipped with an impeller or the like. In the compressor, when the compression ratio increases, the discharging temperature of the compressor rises and the volumetric efficiency declines. Thus, in the turbo compressor included in the turbo refrigerator or the like as described above, the compression of the refrigerant is often performed so as to be divided into a plurality of stages.
In such a turbo compressor, an oil tank for storing lubricant oil, which is supplied to sliding parts of a compression means, is provided. The lubricant oil discharged from an oil pump or the like is led to an oil cooler disposed outside the compressor via an oil piping and is cooled, and is then supplied to the sliding parts such as the respective bearings (for example, see Japanese Unexamined Patent Application Publication No. 7-83526).
Incidentally, in the turbo compressor, an air-tightness test based on Article 7 (6) of Refrigeration Security Rule of High Pressure Gas Safety Act needs to be performed in Japan.
However, in the turbo compressor of the related art, the oil cooler or the oil piping is disposed outside the case of the compressor, whereby the piping is complicated and there are many types of joints, thus the air leakage is not inconsiderable. For this reason, there is a problem in that it is not necessarily easy to meet the standard of the air-tightness test.